A transfer pump generally transfers molten metal out of one furnace to another furnace, into a ladle, or the like. Transfer pumps typically include a motor carried by a motor mount, a shaft connected to the motor at one end, and an impeller connected to the other end of the shaft. Such pumps also include a base with an impeller chamber, the impeller being rotatable in the impeller chamber. Transfer pumps may either be top feed pumps or bottom feed pumps depending, among other things, on the configuration of the base and orientation of the impeller relative to the direction of shaft rotation. Support members extend between the motor mount and the base. The pump may include a shaft sleeve surrounding the shaft, support posts, and a tubular riser. The tubular riser is usually attached to a molten metal outlet opening in the base.
Transfer pumps may be designed with pump shaft bearings, impeller bearings and with bearings in the base that surround the impeller to avoid damage of the shaft and impeller due to contact with the base. The shaft, impeller, and support members for such pumps are immersed in molten metals such as aluminum, magnesium, zinc, lead, copper, iron and alloys thereof. The pump components that contact the molten metal are composed of a refractory material such as graphite or ceramic.
In a transfer pump, the tubular riser extends vertically upward from the molten metal outlet opening of the base and provides a passageway for molten metal. The riser typically extends vertically up to the motor mount from which a conduit in communication with the riser may direct molten metal to a remote location. The end of the tubular riser or pipe may be open for pouring molten metal unidirectionally onto substrates. In a coating operation, molten metal is poured in a stream, like water from a faucet, out of the riser opening towards the substrate. Coating substrates with such transfer pumps is typically slow and difficult due to the time required for the molten metal to drip around to all sides of a substrate or the time required for multiple passes of an object so that all sides are sufficiently coated. Moreover, the coating quality and uniformity of molten metal discharged in this manner onto a substrate are generally poor, the underside coating of the substrate being different than on other sides.